Lexus'05 Phase 3 GS300 - Valves coked up? Diagnose & remedy?

[Prof Prolapse]

I thought perhaps I'd have a punt on the more specialist board before I open it up the wider forums...

I have a 2005 (phase 3 Soap bar shape) Lexus GS300 which I believe has direct injection. Currently at 115,000 miles.

After a frankly incredible run of reliability, it's started to use a little oil (~150ml/1,000 miles but TBC). It's also started noisey tapping from cold, this goes away once it's warmed up. On rare occasions it was a bit rough at idle, I'm unsure whether this is simply slightly low oil. I'm currently monitoring to see if it's using coolant.

Is there a way to diagnose coked up valves without removing the heads?
Is there a cost effective way to remedy this? The car is worth about £2,000, and I have little time to repair it myself.

I am keeping an eye out for HGF, and timing chains/tensioners. But all of these problems effectively write off the vehicle sadly.

Advice appreciated thanks.

[Tabs]

You'll get far more of a response on www.lexusownersclub.co.uk. Good friendly bunch on there.

[swampy442]

Modern cars don't coke valves any more, they run so clean now, with all the fuel additives and lean burn engines.

Tapping is probably just a lifter with a bit of crap in it, have you tried an oil change?

[TommoAE86]

Does this engine have VVTi? My 2GR-FSE has started doing it but apparently there are fixes about to sort it out.

[lexusboy]

If you take the inlet manifold off you can get a good view of a lot of the valves